This invention relates in general to form, fill, and seal packaging machinery of the type in which a continuous sheet of a packaging material is sequentially folded about a series of articles to be packaged, hot or cold sealed about the articles, and cut into individually sealed packages. More specifically, this invention pertains to an improved crimper assembly for forming end seals in overlapping portions of the sheet of packaging material after being folded about an article.
The formation of a plurality of individually sealed packages of articles using a single continuous sheet of a packaging material is well known in the art. Briefly, the sheet of packaging material is initially passed through a folding mechanism, which continuously folds the sheet over on itself to form an enclosure for a series of spaced apart articles. The overlapping portions of the sheet are then sealed along a continuous longitudinal seal. Next, the folded sheet of packaging material is fed to a sealing and cutting assembly, which seals the leading and trailing edges of the folded sheet of packaging material about the enclosed article and cuts the sealing leading and trailing edges so as to form a plurality of individually sealed packages. In some instances, it may be desirable to apply heat during the process of sealing the various overlapping portions of packaging material. Packages produced by this form, fill, and seal process are commonly used for snack bars, candy, cereals, and the like, as well as for other non-food articles.
The sealing of the overlapping end portions of the sheet of packaging material is frequently accomplished by a mechanical crimper assembly. A conventional mechanical crimper assembly includes a pair of opposed crimpers that are disposed on opposite sides of the overlapping portions of the sheet of packaging material. The crimpers are provided with respective undulating or serrated crimping surfaces that are defined by a series of adjacent peaks and valleys. When the opposed crimpers are moved into engagement with the overlapping portions of the sheet of packaging material, the peaks of the first crimping surface on a first one of the crimpers are aligned with the valleys of the second crimping surface on a second one of the crimpers, and vice versa. Such engagement compresses the overlapping portions of the sheet of packaging material to form an intermeshing seal pattern. In some instances, the sheet of packaging material is provided with a cohesive coating for accomplishing the seal when compressed. In other instances, an intermediate seal layer of a coating or other bonding material is provided.
During the crimping and sealing process, it is important that the crimpers exert a sufficient amount of force to compress the overlapping portions of the sheet of packaging material. If an insufficient amount of force is exerted by the crimpers, then the overlapping portions of the sheet of packaging material will not be sufficiently compressed to form a complete seal. At the same time, however, it is important that the amount of force exerted by the crimpers not exceed the strength of the sheet of packaging material. If an excessive amount of force is exerted by the crimpers, the sheet of packaging material will tear or break. Thus, it is desirable that the amount of force that is be exerted by the crimpers against the overlapping portions of the sheet of packaging material remain within a predetermined range to insure a complete and secure seal without causing damage thereto.
In a conventional crimper assembly, the crimpers and the crimping surfaces have been formed from a strong, rigid material, such as high strength steel. Although such crimpers have functioned satisfactorily in the past, several drawbacks have been noted. First, in order to insure that the amount of force exerted by the crimpers against the overlapping portions of the sheet of packaging material remains within the predetermined desired range, the initial set-up of the crimpers on the crimping assembly must be performed very carefully. This set-up operation is very time consuming. Unfortunately, because the set-up operation must usually be repeated whenever it is desired to change from one thickness of the sheet of packaging material to another, this arrangement has been found to be rather inefficient. Second, wrinkles that are occasionally present in the sheet of packaging material can cause additional overlapping portions to be compressed between the opposed crimpers. Because of the rigid nature of the crimpers, the presence of the wrinkles results in an excessive amount of force being applied to the overlapping portions of the sheet of packaging material. Third, in some packages, the number of overlapping layers of the sheet of packaging material varies from side to side. This can occur when the package being formed includes a longitudinally extending fin seal that is folded to one side. Each of the two end seals of the package would thus include a smaller thickness region (composed of only two overlapping portions of the sheet of packaging material) and a larger thickness region (composed of four overlapping portions of the sheet of packaging material). Similar varying thickness regions are found in packages containing conventional gusset folds and fin seals. It has been found to be quite difficult to set-up the two crimpers so as to exert a proper amount of force against these different thickness regions of the end seals. Although it is known to form the crimpers with bowed or recessed areas to accommodate the larger thickness region, such crimpers are more expensive and still suffer from the other drawbacks mentioned above. Thus, it would be desirable to provide an improved structure for a crimper assembly that addresses all of these drawbacks.
This invention pertains to an improved crimper assembly for forming end seals in overlapping portions of the sheet of packaging material after being folded about an article. The crimper assembly includes a crimper including a base, an insert that is formed from a resilient material, and a support plate that is formed from a rigid material. The insert has a surface that is adapted to engage and seal overlapping layers of a packaging material. The insert is disposed between the base and the support plate. The support plate is secured to the body to retain and support the insert thereon. The insert and the support plate may be formed as separate pieces or may be secured together as a single piece. To prevent excessive compression of the insert, the insert can have an aperture formed therethrough, and the support plate can have a protrusion formed thereon that extends through the aperture into abutment with the base. Alternatively, the insert can include a pair of bushings, and such bushings are engaged between the base and the support plate to prevent excessive compression.
Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiments, when read in light of the accompanying drawings.